2. Field of the Invention
The present invention relates to a process for making a carbodiimide-uretonimine-modified polymethylene polyphenylene polyisocyanate composition and urethane foams made therefrom. This invention further relates to producing a carbodiimide-uretonimine-modified polymethylene polyphenylene polyisocyanate composition which has a relatively high two-ring methylene bis(phenylisocyanate) (MDI) content and a viscosity comparable to standard polymeric MDI (PMDI) as is known to those skilled in the art.
This invention further relates to the production of rigid and flexible foams prepared from high two-ring containing carbodiimide-uretonimine-modified methylene bis(phenylisocyanates) which are substantially lighter in color than those prepared from standard viscosity polymethylene polyphenylene polyisocyanates.
2. Description of the Material Art
Narayan et al, U.S. Pat. No. 4,284,730, disclose a liquid carbodiimide, and uretonimine-isocyanurate-containing polyisocyanate composition and microcellular foams made therefrom. The compositions are prepared in the presence of the appropriate catalysts by partially trimerizing a mixture of polyisocyanate and carbodiimide and uretonimine containing polyisocyanates with a trimer catalyst to the desired polyisocyanate levels. Sequential, partial carbodiimization occurs, followed by partial trimerization of a polyisocyanate to the desired free isocyanate level. Another approach is the partial trimerization of a polyisocyanate followed by partial carbodiimization. Yet another approach taught is the simultaneous conversion using a mixed catalyst of carbodiimide and isocyanurate catalyst, to the desired free isocyanate level. Finally, the liquid polyisocyanate is blended with carbodiimide-containing polyisocyanates and isocyanurate containing polyisocyanates to the desired isocyanate level.
The present invention differs from Narayan because the Narayan reference does not contemplate the use of polymethylene polyphenylene polyisocyanates. Moreover, there is no showing in the Narayan disclosure of blending carbodiimide-uretonimine modified polyisocyanates with a two-ring polymeric MDI to obtain a light colored polyisocyanate mixture containing at least 60 percent two-ring MDI content and having a viscosity comparable to a polymeric MDI.
Patton, Jr. et al, U.S. Pat. No. 4,424,288, disclose carbodiimide-modified polymethylene polyphenylene polyisocyanates and their use in the preparation of polyisocyanurate polyurethane foams. The Patton patent teaches a liquid carbodiimide-modified organic polyisocyanate prepared by reacting a crude polymethylene polyisocyanate containing an isomer mixture of 4,4'-, 2,4'- and 2,2'-methylene bis(phenylisocyanate) and an effective amount of a carbodiimidization catalyst. The polyisocyanate/polyurethane foams were made by reacting the modified polyisocyanates with polyols in the presence of various trimerization catalysts.
Patton, Jr. et al differ from the present invention because there is no showing in Patton of mixing the carbodiimide, uretonimine-modified polymethylene polyphenylene polyisocyanates with methylene bis(phenylisocyanate) (MDI) to obtain a mixture with a relatively high two-ring content, i.e. about 60 percent two-ring content, and a viscosity which is comparable to standard polymeric MDI. Further, there is no showing in Patton, Jr. et al of the production of a polyurethane foam packaging material which is substantially lighter in color than polyurethane foams which were possible using carbodiimide-modified polymethylene polyphenylene polyisocyanates of Patton.
Kan, U.S. Pat. No. 3,891,578, discloses carbodiimide isocyanurate foams containing urethane linkages which are characterized by low friability and good flame resistance. The carbodiimide isocyanurate foams are prepared by mixing a polyisocyanate, a polyol and a catalyst system comprising an S-triazine compound and a catalyst which promotes urethane linkages. The present invention differs from Kan et al because there is no showing in Kan of mixing a carbodiimide modified polyisocyanate with a standard two-ring PMDI polyisocyanate mixture to achieve a carbodiimide, uretonimine-modified isocyanurate mixture which contains 60 percent two-ring MDI content and has a viscosity comparable to standard PMDI. Further, there is no showing that it is possible with Kan et al to make a polyurethane foam packaging material which is substantially lighter in color than that possible using standard PMDI alone.